If trekking 75 miles, down plunging hillsides and up painfully steep switchbacks, through the Peruvian Andes doesn't sound like enough of a challenge for you, U.S. Olympian Roberto Carcelen has another idea.

How about running it?

Since 2003, the Peruvian-born runner-turned-Olympic-cross-country-skier has taken groups looking for the ultimate trail run to Peru to follow in the footsteps of the legendary Chasqui Runners -- ancient Inca messengers who ran 100-plus miles per week to deliver fresh fish, letters and gifts throughout the inhospitable Inca empire.

In 2011, his Boulder-based company Inca Runners added a new twist to its already unique offerings, inviting elite athletes, such as ultrarunner Krissy Moehl, and cross country skiing national champion Leif Zimmerman, to lead four or five groups per year.

"We are not on trails that are used by thousands of people on a daily basis," says Carcelen, referring to the overrun official "Inca Trail" leading to Machu Picchu. (Five-hundred people per day now set out on the trail, and permits must be secured at least six months in advance.) "We are taking people places that no one else has been and giving them an opportunity to interact with the culture in a more pure way."

Carcelen grew up running in the massive capital city of Lima, Peru, and didn't discover the vast network of unexplored Inca trails in the Cusco area until his 20s. After a few solo long runs, he fell in love with the views, the lore and the spirituality of the place. He moved there and spent six months scouring the trails solo on foot. Then he started bringing fellow running buddies there, and the seed of an idea was planted.

In 2003, he met his wife Kate online and moved to Seattle to marry her. She taught him how to ski and soon he was training to represent Peru in the 2010 Winter Olympics, making jaunts back to his beloved trails -- paying clients in tow -- to simultaneously train at altitude and earn a living as a guide.

"Training in that high altitude really helped me to boost my fitness and I thought it could help other athletes out as well," says Carcelen, now 41, and eyeing his second Olympic bid.

In recent years, Carcelen teamed up with Hugo Mendez, a running buddy from Lima who now lives in Boulder, to expand Inca Runners' scope and offerings. It now offers week-long trail running and hiking adventures from Choquequirao to Machu Picchu and around other sacred sites like Pisac and Ollantaytambo. It also recently launched a stateside trail running camp in the Grand Tetons.

"There are hundreds of companies that offer the typical hike on the traditional Inca Trail," Mendez says. "But there are none that do what we do."

For more information, visit incarunners.com.